The present invention includes a liquid crystal display device, for example, used for a VTR (Video Tape Recorder) with a camera integrated thereto, a liquid crystal projector and the like, and particularly to a liquid crystal display device having a so-called on chip black matrix (optically compensated birefringence or OCB) structure in which a metal light shielding layer referred to as a black mask is provided on the driving substrate side.
In recent years, as an electronic apparatus with a liquid crystal display device, such as a liquid crystal projector, has been popularized, the liquid crystal display device has increasingly been required to have high performance, and improvement to achieve a liquid crystal display device having higher definition and higher luminance has progressed. Such a liquid crystal display device conventionally comprises a substrate (referred to as a xe2x80x9cdriving substratexe2x80x9d hereinafter) on which pixel electrodes, thin film transistors (TFTs) for controlling the respective electrodes, auxiliary capacitor or capacitance Cs etc. are formed, a substrate (referred to as a xe2x80x9ccounter substratexe2x80x9d hereinafter) on which a color filter (in the case of a color liquid crystal panel), a metal light shielding layer (black mask), etc. are formed, and a liquid crystal layer held between both substrates.
Although the liquid crystal display device having the above construction requires precise alignment between the driving substrate and the counter substrate which are spaced, precise alignment becomes difficult as the definition of pixels increases. Therefore, a so-called on chip color filter structure is proposed in which a color filter is formed on the driving substrate side (refer to Japanese Patent Unexamined Publication No. 254217). In this on chip color filter structure, since the color filter is overlapped with each of the pixel electrodes, no parallax occurs between the pixel electrodes and the color filter, and the effective opening ratio of the pixel portion can be increased, as compared with a conventional structure in which a color filter is provided on the counter substrate side. There is also the advantage that since substantially no error occurs in alignment between the pixel electrodes and the color filter, a high opening ratio can be maintained even if the pixel portion becomes fine. Besides the on chip color filter structure, in order to increase the effective opening ratio of the display device having a so-called on chip black matrix structure has recently been proposed in which a metal light shielding layer (black mask) is also formed on the driving substrate.
FIG. 6 shows a sectional structure of the peripheral circuit portion (including a horizontal driving circuit, a vertical driving circuit, etc.) around the effective pixel portion in a liquid crystal display 100 having the above structure. Like the conventional effective pixel portion, the conventional peripheral circuit portion comprises a liquid crystal layer 118 held between a driving substrate 110 and a counter substrate 120. On the driving substrate 110 is formed a pattern of a polycrystalline silicon film 111 as a semiconductor thin film which constitutes the TFTs, and an insulating film (SiO2) 112 is formed on the polycrystalline silicon film 111. On the insulating film 112 is formed a metal interconnecting layer 113 comprising aluminum (Al). The potential of this metal interconnecting layer 113 is set to potential Vss. On the metal interconnecting layer 113 are laminated in turn interlayer insulating films 114a and 114b. On the interlayer insulating film 114b is formed a metal light shielding layer (black mask) 115 having a pattern reverse to the metal interconnecting layer 113, and a flattening layer 116 is formed on the pattern of the metal light shielding layer 115. On the other hand, on the counter face of the counter substrate 120 is formed a counter electrode 119. The liquid crystal layer 118 is held between the counter electrode 119 and the driving substrate 110.
In the liquid crystal display device 100, the metal light shielding layer 115 on the driving substrate side is set to the same potential as the potential of the counter electrode 119 on the counter substrate side and an auxiliary capacitor or capacitance Cs of the pixel portion. This is a measure for preventing application of a DC voltage to the liquid crystal layer 118 held between the driving substrate 110 and the counter substrate 120. However, not only the effective pixel potion, but also the metal light shielding layer 115 on the peripheral circuit portion are set to the same potential. Therefore, a strong electric field occurs due to a potential difference between the metal light shielding layer 115 and the metal interconnecting layer (Al wiring layer) 113 at potential Vss, and impurity ions present in the periphery are attracted. As a result, water chemically reacts with aluminum (Al) on the cathode (the metal interconnecting layer 113) side, thereby causing disconnection due to corrosion of aluminum. The metal light shielding layer 115 on the peripheral circuit portion is formed in a pattern reverse to the metal interconnecting layer 113 under the metal light shielding layer 115, i.e., so that both layers do not overlap each other, as viewed from the upper side. Therefore, in a portion where the pattern of the metal light shielding layer 115 is absent, incident light is cut off by the metal interconnecting layer 113. Thus, in a portion where the pattern of the metal interconnecting layer 113 is large, large quality of light is incident, and the above chemical reaction of aluminum is accelerated by light and heat, thereby more easily causing disconnection. Further, this disconnection allows light irradiation of the active layer 11 of the thin film transistors (TFTs) provided under the metal interconnecting layer 113, and thus has an adverse effect on the operation, such as variation in operation points of the TFTs. Particularly, when the liquid crystal display device 100 is used for a projector or the like, this brings about a large problem with respect to reliability. When electrical leakage from the metal interconnecting layer 113 of the peripheral circuit portion occurs, the liquid crystal display device 100 becomes defective regardless of the position of leakage.
The present invention has been achieved in consideration of the above problems, and an object of the invention is to provide a liquid crystal display device which is capable of suppressing occurrence of an electric field between a metal light shielding layer and a metal interconnecting layer in the peripheral circuit portion to prevent disconnection of the metal interconnecting layer, and which has improved reliability under conditions where light and heat are present.
In order to achieve the object, in accordance with an aspect of the present invention, there is provided a liquid crystal display device comprising a first substrate in which a pixel portion having a plurality of pixel electrodes, and a peripheral circuit portion disposed around the pixel portion are formed, and which comprises a metal interconnecting layer provided in the peripheral circuit portion and set to a second potential, and a metal light shielding layer which is selectively provided in a pattern reverse to the metal interconnecting layer in each of regions of the pixel portion and the peripheral circuit portion, and which is set to a first potential in a region corresponding to the pixel portion and set to the second potential in a region corresponding to the peripheral circuit portion; a second substrate disposed opposite to the first substrate with a predetermined space and having a counter electrode set to the first potential; and a liquid crystal layer held between the first and second substrates. The liquid crystal display device further comprises a transparent electrode formed on the metal light shielding layer of the peripheral circuit portion and set to the first potential.
In accordance with another aspect of the present invention, there is provided a liquid crystal projector comprising a liquid crystal panel comprising a first substrate in which a pixel portion having a plurality of pixel electrodes, and a peripheral circuit portion ,disposed around the pixel portion are formed, and which comprises a metal interconnecting layer provided in the peripheral circuit portion and set to a second potential, and a metal light shielding layer which is selectively provided in a pattern reverse to the metal interconnecting layer in each of regions of the pixel portion and the peripheral circuit portion, and which is set to a first potential in a region corresponding to the pixel portion and set to the second potential in a region corresponding to the peripheral circuit portion; a second substrate disposed opposite to the first substrate with a predetermined space and having a counter electrode set to the first potential; and a liquid crystal layer held between the first and second substrates; and optical means for applying light to the liquid crystal panel and enlarging and projecting transmitted light from the liquid crystal panel.
In accordance with a further aspect of the present invention, there is provided a liquid crystal display device comprising a first substrate in which a pixel portion having a plurality of pixel electrodes, and a peripheral circuit portion disposed around the pixel portion are formed, and which comprises a metal interconnecting layer provided in the peripheral circuit portion and set to a second potential, and a metal light shielding layer which is selectively provided in a pattern reverse to the metal interconnecting layer in each of regions of the pixel portion and the peripheral circuit portion, and which is set to a first potential in a region corresponding to the pixel portion and set to an electrically floating state in a region corresponding to the peripheral circuit portion; a second substrate disposed opposite to the first substrate with a predetermined space and having a counter electrode set to the first potential; and a liquid crystal layer held between the first and second substrates.
In accordance with a still further aspect of the present invention, there is provided a liquid crystal display device comprising a first substrate in which a pixel portion having a plurality of pixel electrodes, and a peripheral circuit portion disposed around the pixel portion are formed, and which comprises a metal interconnecting layer provided in the peripheral circuit portion and set to a second potential, and a metal light shielding layer which is provided over the entire surface of the peripheral circuit portion to prevent entrance of light into the metal interconnecting layer, and which is set to a first potential; a second substrate disposed opposite to the first substrate with a predetermined space and having a counter electrode set to the first potential; and a liquid crystal layer held between the first and second substrates.